Administrator’s Command Line Guide

Chapter 6. Maximizing Storage Cluster Performance
• -s vstorage1.example.com is the hostname of the computer where the vstorage-hwflush-check
server is running.
• -d /vstorage/stor1-ssd/test defines the directory to use for testing data flushing. During its
execution, the client creates a file in this directory and writes data blocks to it.
• -t 50 sets the number of threads for the client to write data to disk. Each thread has its own file
and counter. You can increase the number of threads (max. 200) to test your system in more
stressful conditions. You can also specify other options when running the client. For more
information on available options, see the vstorage-hwflush-check man page.
3. Wait for 10-15 seconds or more and power off the computer where the client is running, and then turn
it on again.
Note: The Reset button does not turn off the power so you need to press the Power button or
pull out the power cord to switch off the computer.
4. Restart the client by executing the same command you used to run it for the first time:
# vstorage-hwflush-check -s vstorage1.example.com -d /vstorage/stor1-ssd/test -t 50
Once launched, the client reads all written data, determines the version of data on the disk, and then restarts
the test from the last valid counter. It then sends this valid counter to the server, and the server compares it
with the latest counter it has. You may see output like:
id<N>:<counter_on_disk> -> <counter_on_server>
which means one of the following:
• If the counter on disk is lower than the counter on server and a “cache error detected” message is
returned, it means that the storage device has failed to flush the data to disk. Avoid using this storage
device in production—especially for CS or journals—as you risk losing data.
• If the counter on disk is higher than the counter on server, it means that the storage device has flushed
the data to disk but the client has failed to report it to the server. The network may be too slow or the
storage device may be too fast for the set number of load threads so you may consider increasing it.
This storage device can be used in production.
• If both counters are equal, it means the storage device has flushed the data to disk and the client has
reported it to the server. This storage device can be used in production.
To be on the safe side, repeat the procedure several times. Once you check your first storage device,
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